At the present time four-high stands have been designed, structured and made to process only wide flat products and cannot be employed, when so required, as universal stands too.
Likewise, universal stands have been designed, structured and made to process sections, such as I-beams and sections with a normal or wide flange or other sections such has H-beams, but cannot be suitable to process wide flat products and therefore to perform the functions of a universal stand.
The need to have not two separate rolling lines but to be abel to have in the same line and with the same stands both four-high stands and universal stands and vice versa has been felt for some time now.
This need is mainly felt on economical grounds and is linked firstly to the processing of small lots, where the need to obtain swift changes of the product to be manufactured has become urgent, and secondly to the instability of the market with its high and low points of demand, now for one type of product and now for another type.
Each of these plants involves requirements of investment, space occupied and embodiment of plants, and it is unthinkable that two specialized plants should be set up, one for one type of product and the other for another type of product, and should then be underemployed and used only part-time.
On the other hand, considerable technical problems are involved in embodying a rolling stand which can process both wide flat products and also I-beam sections or the like.
It is enough to think of the substantial differences in the rolling rolls and in their composition so as to understand the technical, technological and conceptual problems which hinder such an embodiment.
Documents FR-A- No. 2.541.600, JP-A- No. 54139866, DE-A- No. 1,937,368, U.S. Pat. No. 3,319,450 and EP-A- No. 0,166,478 refer to rolling stands which can be converted from universal stand into two-high stand and vice-versa.
None of said documents provides for the possibility of converting an universal stand into a four-high stand.
Furthermore, the rolling stands disclosed in said documents are of relatively complicated use, owing to the plurality of elements which they comprise; the substitution of the rolls is always a slow and difficult operation.
Document JP-A- No. 62114706 discloses a rolling stand which can be converted from an universal stand into a two-high and/or a four-high stand and vice-versa, according to the preamble of claim 1.
This kind of stand is provided with fixed roll standards forming, by pairs, a frame into which the different rolls are laterally inserted.
Said rolls are inserted in the spaces comprised between the standards by means of a laterally movable carriage, causing a remarkably large lateral bulk of the whole roll stand.
Furthermore, all the rolls must necessarily be provided of their housings and of the elements for journaling them to the standards, prior to the insertion into the standards.
Owing to the fixed spatial disposition of the roll standards, only rolls having particular dimensions may be used, and in the case of a stand converted into a four-high stand, the wide flat strips which are produced may obviously not have a width which goes beyond the distance between the roll standards.